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Growth mechanisms in dinosaur eggshells

Another new paper from the last JVP

Moreno-Azanza, M. , E. Mariani , B. Bauluz & J.I. Canudo. 2013. Growth
mechanisms in dinosaur eggshells: an insight from electron backscatter
diffraction. Journal of Vertebrate Paleontology, 33(1): 121-130.


ABSTRACT. The direct relationship between eggshell structure and
eggshell formation is well established for avian eggs, but has never
been studied in depth in non-avian dinosaurs. Both biological and
crystallographic mechanisms take part in eggshell formation, due to
its dual mineralogical and proteinaceous nature, but the exact
relative contributions of these processes are still poorly known.
Competitive growth has been postulated to be the general mechanism
leading to the characteristic columnar construction seen in dinosaur
eggshell. Here we analyze the eggshell structure of both ornithopod
and non-avian theropod ootaxa with orientation contrast imaging and
electron backscatter diffraction and present the first misorientation
angle boundary maps of fossil eggshell, in order to ascertain whether
competitive growth can explain the development of the columnar
structure in non-avian dinosaur eggshell. Our results show that both
eggshell types can be constructed via competitive growth, and that
small changes in organic core spacing and crystal grain size, which
are organically controlled, may develop into major changes in general
eggshell structure, which will determine the physical properties of
the egg. However, interseed distance cannot be directly correlated
with organic core spacing as the competitive growth model predicted.

Jose Ignacio Ruiz-Omenaca
Museo del Jurasico de Asturias (MUJA)
E-33328 Colunga, Spain